Cement compositions



Patented Dec. 30, 1947 UNITED STATES PATENT OFFICE CEMENT COMPOSITIONSRichard 11. Grant, San Francisco, Calif., assignor l" to PermanenteCement Company, Oakland, Calif., a corporation of California No Drawing.Application January 24, 1945, Serial No. 574,440

3 Claims.

This invention relates to a plastic cement, particularly one having aPortland type cement base, and is continuation-in-part of my copendingapplication Serial No. 502,195, filed September 13, 1943, now abandoned.

One of the principal problems that has confronted the building industryfor many years has been the inability to obtain a weather-proof plasterwhich would adhere to paper covered lath or the like. such as gypsumplasterboard lath, and at the same time have the other characteristicsof a desirable plaster. Another problem which has also presented aconsiderable disadvantage has been the lack of a satisfactory plaster orplastic cement of a Portland cement base which would adhere to papercovered lath or the like.

It is among the objects of the present invention to overcome the aboveand other problems and disadvantages by providing a plastic cementhaving a Portland type cement base, which cement is particularly usefulas a plaster or mortar.

According to the invention there is provided a dry homogeneous mixtureof a plastic cement comprising Portland and an additive of asbestosfibre calcium chloride, hydratgg lime and an a aine earth metal soap.The quantitles of Portlan cemen to a 1 1Y8 may vary between abouteighty-five to ninety-five pounds of Portland cement to about five tofifteen pounds of additive. The preferred mix is about ninety pounds ofPortland cement to about ten pounds of additive.

The basic constituents of the additive are cal- ,cium chloride andasbgstos. The quan y of caldium hloride in the cement should be belowabout three pounds to each 100 lbs. of Portland cement and is preferablyat least one pound to each ninety pounds of cement, The quantity ofasbestos may vary between about 5 pounds and about pounds to each 100pounds of the final composition, with 6 pounds being preferred.

The preferred composition of the additive includes 1 pound ofcrystalline calcium chloride, 6 pounds of asbestos fibre, 3 pounds ofhydrated lime, and 1 ounce of an alkaline earth metal soap such ascalcium stearate.

In the a sbestos is useful because of its unique water retainingability, its expansion factor when dehydrating to offset cementshrinkage, and as a plasticizer. The crystalline calcium chlorideincreases the initial strength of the mortar and in combination with theother materials acts as an adhesive agent. The hydrated lime addsworkability and plasticity. The alkaline The additive may be blendedwith the Portland cement in such manner as will yield a homogeneousmixture. In practice it is useful to grind the calcium chloride,asbestos fibre, hydratelflime and calcium stearate or other alkalineearth metal soap together and the p mimthe resultant finely divided masswiththe' Portland cement. The

mixing of the finely divided additive and the Portland cement may beeflected byblowifii the materials intolih" air cyclone cylinder whichincludes one or more paddle agitators (such as a Straub' mixingmachineltoinsure complete intermixing and cement cgatinggf each particleof the admixture, particularly of the finely ground calcium chloride. Inalternative procedures the Portland cen e i t and the constituents ofthe saga-Na can be groun d togct her at one time either by firstpreparl'fig the homogeneous mixture of calcium chloride, asbestos fibre,hydrated lime and alkaline earth metal soap and adding it to the rawement clinker, or by adding the constituents of the aadit1'v"'lne theraw state to the cement clinker and mtgrgrinding themallsimultaneouslyTalc may bFuse'd as a grinding 'a'id ih 'arlylif these procedures. Thepreferred practice is to intergrind each of the raw materialssimultaneously.

However, regardless of the procedure employed, it is essential to thepresent invention that the composition of the additive be incorporatedwith the cement under such conditions that the cement coa he particlesof the additive so as to form a dry, finely divided, homogeneous mass.The additive is not an "admix in the sense that it can be incorporatedin a cement mixer with the cement, aggregate and water. Variouscompositions have been proposed heretofore and termed "admixes. However,these are added to the cement mixture along with the sand, cement, andwater and are only conditioned with the cement in the mixer. Such amethod of mixing is unsatisfactory because the ingredients are :1sufficiently blended and interdispersed to provide necessary-adhesionand plasticity which are among the objects of the invention.

I have found that finely divided dry homogeneous mixture of calciuhydrated J1me, fibrous asbestos and calcium stearate lntimately groundto a fin e powdered state If a Ball n'ifihor a stoneiniill and mixedwith a P ceirlfitiifdtiids a plastidcefiinfpossessing the renewingdesirable characteristics:

For example:

The composition of this additive and Portland earth metal soap acts as awater-proofing agent. 66 type cement mixed with a relatively largevolume of sand (3% to 4 volumes of sand to 1 volume of the compositionof the invention) can be hydrated with a minimum amount of water to forma very plastic, workable plaster or mortar, which, when applied to awall or ceiling surface. does not check, crack or craze. Because of theincreased sand-carrying capacity of this material the shrinkage, commonto Portland cement, is offset by this composition.

A plaster made f Portland cement and this composition, to which is added2 /2 to 3 volumes of sand and suilicient water to form a workable,plastic plaster, will adhere to and bond with ordinary gypsum plasterlath, something which no Portland cement plaster would do heretofore.Because of the presence of the asbestos fibre, hydrated lime and calciumchloride, the water retention ability of this composition insures a moreeven and proper cure than before attained with ordinary Portland cementmortar, This is indicated by the following: Two series of test blockswere made utilizing equal parts of sand, water and Portland cement inone case and, in the other, a cement containing the material of thepresent invention. The blocks were stored in a room having constanttemperature and humidity and were weighed at regular intervals. Thoseblocks including the composition of this invention did not dehydratenearly as rapidly as the blocks containing only Portland cement andsand.

30 A compression test of all the blocks after seven days of curingshowed the blocks containing the composition of this invention to haveconsiderably more strength than the blocks without this composition.

A further advantage of the composition of this invention is the entireelimination of the formation of a hard skin or surface, on the plasteredwall, while the mass remains pulpy or soft below this hard skin,resulting in a weak, undercured wall. This material may be mixed intoplaster or mortar in a central mixing plant and distributed in volume bytrucks or other carriers to workmen on the job where the plastic plastercan be held in mortar boxes from 1 to 3 hours and still be highlyplastic and workable. If a slight initial set occurs during this period,the mortar can be retempered with a small amount of water and stirring,returning the plaster to l fs1ln1 ar 0 an'alkaline earth metal soap maysatisfactorily be used in the composition of the invention in place ofthe alkaline earth metal soap.

What is claimed is: 1. A plastic cement composition for use on papercovered lath comprising, a dry, finely divided mixture of the following:

1 Parts Portland cement 90 Calcium chloride 1 Asbestos 6 Hydrated li 32o Alkaline earth metal soap less than 0.1

2. An additive for incorporation into a dry, finely divided Portlandcement comprising the following composition:

- Part 25 Calcium chloride 1 Asbestos 6 Hydrated l 3 Alkaline earthmetal soap less than 0.1

35 by weight of an alkaline earth 3. An additive for incorporation intoa dry, finely divided Portland cement consisting of from 1 to 3 parts byweight of calcium chloride, from 5 to 10 parts by weight of asbestos,about 4 parts by weight of hydrated lime, and less than 0.1 part metalsoap.

RICHARD H. GRANT.

REFERENCES CITED 0 The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

